Downhole tools are controlled from the surface or locally by control systems to move a component between two or more positions. The movable components are exposed to highly variable tubing pressures and can be constructed in ways where pockets that trap pressure at some pressure level can form with a resulting high differential pressure across a tool component that is high enough to prevent the normal actuation system from operating the tool into another position.
One example of such a tool is a barrier valve that uses a 90 degree rotating ball. In some designs the ball turns between opposes seats that can have a resilient seal in contact with the ball. The actuation system can be in part in an annular space that is in communication with the passage in the ball around its pivot axis. When the valve is open tubing pressure and the annular space equalize through the small passage around the ball pivot axis. The ball can be closed during a time when the tubing pressure is low. Thereafter with the ball in the closed position and the annular space around the ball and the passage in the ball isolated from tubing pressure, pressure can build on the ball under conditions where the differential across the ball from tubing to the annular space results in increased contact frictional force so that the mechanism that would rotate the ball under normal operation is not strong enough to turn the ball back to the open position. Merely adding pressure above the ball during these circumstances just increases the differential across the ball with respect to the annular space and aggravates the contact loading problem.
The present invention in its various embodiments addresses this problem by equalizing pressure into the annular space by separation of a ball from its uphole seal in a rotating ball environment for a downhole valve. Other applications where trapped low pressures create loading to the point where the tool will not move normally are envisioned.
Equalizing devices in downhole tool and more particularly flapper type safety valves are well known as shown in Fineberg U.S. Pat. No. 4,478,286 and which included a spring loaded plug in the flapper that is actuated by a flow tube. Other equalizing devices are shown in U.S. Pat. Nos. 7,204,313; 6,848,509; 3,799,204; 6,644,408; 6,296,061; 6,283,217; 6,079,497 and 5,752,569. These valves generally have an equalizing valve built into a flapper to be actuated by the advancing flow tube before the flow tube tries to move the flapper. Alternatively the valve can be built into the housing to equalize across a closed flapper as a result of initial flow tube movement that occurs before the flow tube engages the flapper.
While the objective of the present invention is equalization to enable operation when large pressure differentials are present, its execution of that objective is different from the above described equalizing mechanism. Rather, in one embodiment a tool is delivered to the downhole tool needing pressure equalization. The tool is anchored and actuated to separate two members that are in sealing contact using built in flexibility of these parts to move relatively to each other. There after the tool is released and removed. It can be delivered quickly by wireline with a jar actuated to operate the tool or in another embodiment it can be delivered on coiled tubing and respond to pressure applied through the coiled tubing to operate. It can be released with a pickup force on the coiled tubing. Other embodiments are envisioned. Those skilled in the art will more fully appreciate the various aspects of the present invention by reviewing the descriptions of the embodiments described below in conjunction with the associated drawings while recognizing that the full scope of the invention is found in the appended claims.